Better tyke a stress pill, Dyve
In "2001: A Space Odyssey" (1968), HAL was to be called Athena and have a female voice. According to Keir Dullea (Dave Bowman), Nigel Davenport and Martin Balsam were hired and later replaced before Douglas Rain finally landed the role of HAL. Davenport was actually on-set in England during filming, reading HAL's lines off-camera so that Dullea and Gary Lockwood could react to them. Apparently, Stanley Kubrick thought that Davenport's English accent was too distracting, so after a few weeks he dismissed him and for the remainder of the shoot HAL's lines were read by an assistant director who, according to Dullea, had a Cockney accent so thick that lines like "Better take a stress pill, Dave" came out like "Better tyke a stress pill, Dyve". Later Balsam was hired and recorded HAL's voice in New York, but again when Kubrick heard his lines he wasn't satisfied, so he finally got Rain to re-record everything during post-production. Rain recorded in Canada, speaking his lines barefoot with his feet resting on a pillow to get the relaxed tone. For the sequel, Peter Hyams' 2010, the opposite process was used: Rain recorded all of HAL's dialogue during pre-production prior to principal photography. That's why, to this day, Dullea and Rain have never actually spoken directly to each other or met in person. - IMDB
The HAL 9000 is number 15 on our "Top 100 Monsters Of Movie And Television" list!